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Abstract:

There is disclosed a process for manufacturing an in-mould labelled
article, the process comprising the steps of: placing a label comprising
a polyvinylidene chloride coated film (15) into a mould for injection
moulding, thermoforming, or blow moulding; holding the label in position;
injecting a polymeric melt into, or thermoforming or blowing a polymeric
preform in said mould so as to bind with the label; and removing the
article from the mould. A process of in-mould labelling using a label
comprising a polyvinylidene chloride coated film is also disclosed.

Claims:

1. A process for manufacturing an in-mould labelled article, the process
comprising the steps of: placing a label comprising a film coated with a
polyvinylidene chloride (PvdC) coating into a mould for injection
moulding, thermoforming, or blow moulding; holding the label in position;
injecting a polymeric melt into, or thermoforming or blowing a polymeric
preform in the mould, wherein the polymeric melt or polymeric preform
binds to the label and forms a labelled article; and removing the
labelled article from the mould, wherein the label is oriented in the
mould so that the PvdC coating on the film lies on or towards an exterior
surface of the label when retrieved from the mould, and wherein the PvdC
coating on the film is shielded from the melt during the process by
interposing between the coating and the melt during the process a
substrate layer of the film.

2. The process according to claim 1, wherein the melt or preform does not
contact the exterior surface of the label.

3. The process according to claim 1, wherein the label is held in
position by at least one of a vacuum, compressed air and static
electricity.

4. The process according to claim 1, wherein the label is placed into the
mould by at least one of feeding the label into the mould by means of a
belt, the label falling under gravity from a magazine into the mould, and
placing of the label by a handling unit, optionally a robot.

5. The process according to claim 1, wherein the label covers at least
about 50% of the entire outer surface of the article.

6. The process according to claim 1, further comprising providing the
mould at a lower temperature than that of the melt.

7. The process according to claim 1, wherein the PvdC coating is
printable.

8. The process according to claim 7, further comprising printing on the
PvdC coating after removal of the labelled article from the mould.

9. The process according to claim 1, wherein the PvdC coating is printed
with a heat-resistant ink.

10. The process according to claim 1, wherein the PvdC coating has a coat
weight of at least about 1 gsm.

11. The process according to claim 1, wherein the PvdC coating has a coat
weight in the range of from about 1.5 gsm to about 4 gsm.

12. The process according to claim 1, wherein the film further comprises
a transparent inorganic coating to enhance its barrier properties.

13. The process according to claim 12, wherein the transparent inorganic
coating comprises a metal or metalloid oxide or nitride.

14. The process according to claim 13, wherein the transparent inorganic
coating comprises an aluminum or silicon compound.

15. The process according to claim 1, wherein the labelled article is
formed by injecting a polymeric melt into the mould.

16. The process according to claim 1, wherein the labelled article is
formed by thermoforming a polymeric preform in the mould.

17. The process according to claim 1, wherein the labelled article is
formed by blowing a polymeric preform in the mould.

18. The process according to claim 1, wherein the label is held in
position by a vacuum.

19. The process according to claim 1, wherein the label is held in
position by compressed air.

20. The process according to claim 1, wherein the label is held in
position by static electricity.

Description:

[0002] The present invention relates to a process for manufacturing an
in-mould labelled article using a label comprising a polyvinylidene
chloride coated film.

BACKGROUND

[0003] The technique of in-mould labelling (IML) has been known for many
years. It involves the use of paper or plastics labels which ultimately
form an integral part of the moulded product. The in-mould labels must,
therefore, be able to tolerate the heat applied during the moulding
process. The resultant product is a pre-decorated item, such as a
container or the like, which may be filled thereafter. In contrast to
glue applied or pressure-sensitive labels which appear above the surface
of the container, in-mould labels appear as part of the container.
Effectively, in-mould labelling eliminates the need for a separate
labelling process following the manufacture of the container, which
reduces labour and equipment costs.

[0004] In-mould labels generally comprise a carrier base, consisting of a
polymeric or cellulosic carrier film, on which a decorative pattern or a
written message is printed. The thus obtained label is subsequently
positioned against a wall of a mould for injection moulding or for blow
moulding or the like, held in place by various means, such as
electrostatic forces or vacuum suction, and a polymeric article is
moulded by injecting a mass of polymeric melt or by blowing a polymeric
parison against the mould walls on which the in-mould label is applied.
The adhesion of such labels to the polymeric article can be enhanced by
applying a heat sealable layer (a film or a coating) onto the backing
side (i.e., not printed surface) of the in-mould label which is to be in
contact with the polymeric article.

[0005] In-mould labels can be used to cover a portion of a container or to
cover the entire outer surface of a container. In the latter case, the
in-mould label serves as an additional layer and may, therefore, enhance
the structural integrity of the container.

[0006] Laminate films or multi-layer films are also well known and have
particular packaging applications in the food industry, and
pharmaceutical, medical and health care products. An important aspect of
laminate films when used in packaging food, for example, is to prevent
the ingress of moisture and air into the container which would otherwise
cause the food therein to degrade undesirably quickly.

[0007] To counteract this effect, US 2009/0061062 describes a multilayer
film having an active oxygen barrier and at least one layer containing an
iron-based scavenging composition. In particular, ethylene vinyl alcohol
copolymer (EVOH) is known as a good oxygen barrier material, and is
widely used in conjunction with multi-layer packaging films. Oxygen
barrier materials are employed in retort processes such as retort
sterilisation and retort cooking. In retort processes, heat and pressure
are used to cook or sterilise food in a sealed package. Retort conditions
can be demanding with temperatures typically ranging from 115° C.
to 130° C. under pressurised steam. However, under these retort
conditions, many oxygen barrier polymers including EVOH can become
damaged, distorted, delaminated, or they may lose their oxygen barrier
properties during or after retorting due to absorbed moisture. The Oxygen
barrier properties of the EVOH layer of a multi-layer film are reduced if
exposed to high humidity. Therefore, the EVOH layer is usually protected
by an outer layer that has good moisture barrier properties (such as
polypropylene). However under the high temperature conditions experienced
during the retort process, the moisture barrier properties of the
protective layer is dramatically reduced. This phenomenon is known as
"retort shock" in which moisture is trapped in the oxygen barrier layer,
such as EVOH, during the retort process--thus leading to a drop in the
barrier properties of the EVOH layer so as to allow the ingress of oxygen
into the container.

[0008] There is a need for an article, such as food packaging or the like,
involving in-mould labelling which does not suffer from the
above-mentioned disadvantages. From the description that is to follow, it
will become apparent how the present invention addresses the
above-mentioned deficiencies associated with prior art constructions,
while presenting numerous additional advantages not hitherto contemplated
or possible with prior art techniques.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Embodiments of the present invention will now be described, by way
of example only, with reference to and as shown in the accompanying
drawings, in which:

[0010] FIG. 1: is a graph illustrating weight loss of PvdC at low
temperatures under nitrogen.

[0011]FIG. 2: is a graph illustrating weight loss of PvdC at low
temperatures in air.

[0012]FIG. 3: is a graph illustrating weight loss of PvdC recast from THF
and THF/Water, under nitrogen.

[0017]FIG. 8: is a schematic drawing of PvdC coated laminate film which
can form at least part of a label for an in-mould labelling process
according to the invention.

[0018]FIG. 9: is an alternative PvdC coated laminate film which can form
at least part of a label for an in-mould labelling process according to
the invention.

DETAILED DESCRIPTION

[0019] According to a first aspect of the present invention, there is
provided a process for manufacturing an in-mould labelled article, the
process comprising the steps of:

[0020] placing a label comprising a polyvinylidene chloride (PvdC) coated
film into a mould for injection moulding, thermoforming, or blow
moulding;

[0021] holding the label in position;

[0022] injecting a polymeric melt into, or thermoforming or blowing a
polymeric preform in said mould so as to bind with the label; and

[0023] removing the article from the mould,

wherein the label is oriented in the mould so that the PvdC coating on
the film lies on or towards the exterior surface of the label when
retrieved from the mould, and wherein the PvdC coating on the film is
shielded from the melt during the process by interposing between the
coating and the melt during the process a substrate layer of the film.

[0024] The film may have a monoweb or laminate structure, whether by
coextrusion, lamination, extrusion coating or further or alternative
coating, or any combination thereof. The label must comprise at least a
substrate material and a PvdC coating thereon.

[0025] The PvdC coating on the film of the in-mould label allows the label
to retain its oxygen barrier properties during and after a retort
sterilisation or cooking process, during which conditions of high
humidity are likely to be encountered in the mould. The PvdC coating
inhibits the ingress of oxygen therethrough even under such high humidity
conditions. In this way, the problem of retort shock is addressed. One
advantage of this is to extend the shelf life of products retained in
packaging which undergo retort sterilisation or cooking processes.

[0026] It could be considered counter-intuitive to employ a compound
comprising chlorine for use during high temperature processes such as
in-mould labelling due its degradation leading to potential toxicity or
environmental issues. For example, it may be expected that chlorine would
be liberated in the form of HCl at the elevated temperatures used during
the moulding process but, contrary to expectation, we have found that
PvdC does not undergo dehydrochlorination under these conditions, as is
shown by the experimental data below.

[0027] As will be explained in the experimental section, PvdC appears to
undergo dehydrochlorination at temperatures of approximately 200°
C. However, typical in-mould conditions also may comprise temperatures at
around this level, or higher. Consequently, it might be thought that an
in-mould labelling process utilising a PvdC coating would risk liberating
HCl in the process. We have found, however, that such risks can be
avoided by shielding the PvdC coating to some extent within the mould.

[0028] In a typical in-mould labelling process the mould itself is chilled
so that the molten polymer supplied to the mould cools and hardens
rapidly against the mould surface once injected. Typical in-mould
temperature conditions are from 191-232° C. for the melt, and
32-66° C. for the mould.

[0029] We have found that by providing the in-mould label as a PvdC-coated
substrate, and by using the substrate to shield the coating from the high
temperatures of the melt during coating, we can prevent the PvdC coating
from reaching its decomposition temperature, or from doing so for long
enough to decompose.

[0030] Consequently, in the process according to the invention, the label
is oriented in a mould so that the PvdC coating on the film lies on or
towards the exterior surface of the label when retrieved from the mould.

[0031] Thus, when the label comprises a substrate material and a PvdC
coating thereon, in the mould the PvdC coating lies between the substrate
and the mould exterior. Typically the mould will be chilled and will
receive in use a molten polymeric material for moulding into the form of
a container or other article. The molten polymeric material may have a
high temperature--for example above 200° C. when it enters the
mould, and if directly exposed to such temperatures for a prolonged
period of time, the PvdC coating may dehydrochlorinate. However, we have
found that if the PvdC coating is protected from such direct exposure by
the presence of the substrate material of the label (e.g. polypropylene)
lying between the coating and the molten material as it enters the mould,
no such dehydrochlorination occurs. This may be explained by one or more
of the following: [0032] The substrate protects the PvdC coating from
decomposition by performing an insulation function; [0033] The chilled
mould helps to keep the PvdC coating below decomposition temperature
during the moulding process; [0034] The moulding process is sufficiently
rapid that decomposition of the PvdC does not occur in the time
available, before the molten material supplied to the mould cools down.

[0035] Preferably, the label has an outside which faces the mould exterior
in the process of the invention, and an inside which faces the mould
interior in the process of the invention. When molten material is
injected into the mould it makes contact with the inside of the label,
but preferably not the outside. Preferably, the PvdC coating on the label
lies at or towards the outside of the label.

[0036] Preferably the label comprises the PvdC coating and a substrate
material, the thickness of the substrate material being at least about 15
μm, preferably at least about 20 μm, more preferably at least about
30 μm and most preferably at least about 40 μm. Generally speaking,
the thicker the substrate, the better its ability to insulate the PvdC
coating against heat from the molten material entering the mould, but
such considerations must be tempered by considerations such as cost,
functionality and aesthetics.

[0037] It is well known in the art [see for example Thermal stabilisation
of poly(vinyl chloride) by organotin compounds--Polymer Degradation and
Stability, Volume 88, Issue 1, April 2005, Pages 46-51] that certain
additives can be used to delay the onset of dehydrochlorination of PvdC.
In the present invention, such additives may optionally be incorporated
into the PvdC coating to provide additional thermal stabilisation of the
coating.

[0038] Barrier properties of the film used in the in mould labelling
process of the invention may be further improved by the inclusion in or
on the film of a transparent inorganic coating. Suitable inorganic
materials include metal and metalloid oxides and nitrides such as silicon
oxides (SiOx), aluminium oxides (AlOx), silicon nitrides
(Si3N4) provided together with carbon, hydrogenated versions of
silicon nitride, and mixtures of two or more thereof. Suitable techniques
for depositing such coatings on the film include vapour deposition,
physical vapour deposition (PVD), plasma enhanced chemical vapour
deposition (PECVD), dielectric barrier discharge or magnetron or radio
frequency generated plasma electron beam evaporation sources, induction
heated evaporation sources, magnetron sputter deposition sources and
atomic layer deposition (ALD)

Thermogravimetric Analysis of PvdC Coatings

[0039] Summary:

[0040] Analysis has shown there is a slight weight loss around 130°
C. for PvdC lattices; the evidence to date suggests that this may be
water. A second and more significant weight loss occurs around
200° C. which coincides with dehydrochlorination.

Introduction

[0041] Films with a PvdC coating were evaluated for use as in-mould
labels. In use in in-mould labeling, such films are likely to be
subjected to relatively high temperatures--for example temperatures of
from 100° C. to 150° C. --and this evaluation was intended
to ascertain whether at such temperatures, thermal degradation would be
experienced. Accordingly a screen of three PvdC lattices was carried out
using thermogravimetric analysis (TGA).

Experimental

[0042] Filmic samples of PvdC, cast from THF, were placed in an aluminium
dish and left to air dry for about two months. Samples of this dried
material were taken and the weight loss profile as a function of
temperature determined.

Thermogravimetric Analysis in Nitrogen--Results

[0043] Samples of approximately 10 mg were heated at 10° C./minute
in nitrogen, with air introduced at 750° C. from which the onset
temperature and weight loss have been calculated. FIG. 1 shows a pyrogram
of the data of table 1 below.

[0045] Under nitrogen a small weight loss was observed above 130°
C. (see FIG. 1). This weight loss was also observed to a similar
magnitude in air (see FIG. 2). The temperature at which this small weight
loss occurs is higher than would usually be expected for liberation of
water, but this may be a function of the fact that the samples were air
dried over a long period of time, and so some residual locked-in moisture
may have remained in the dried samples.

[0046] To test this theory, a further sample was cast from THF and water,
and re-tested as above. The first weight loss from this sample was seen
to increase in magnitude, and at a slightly lower temperature of around
100° C. A similar sample re-cast from THF only also gave a slight
rise in the magnitude of this weight loss, but less so than the sample
with added water (see FIG. 3). Considering THF is highly miscible with
water and hence shows some hygroscopic tendencies, this increase may be
attributed to water. Overall this evidence suggests the minor weight loss
just above 100° C. is associated with water bound within the
matrix.

[0047] The major weight loss for these materials occurs around 200°
C., with this equating to 73% of the sample matrix under nitrogen, which
is consistent with the 75% expected for dehydrochlorination. From FIG. 4,
it appears that this occurs as a two step process prior to the loss of
any carbonaceous residue on introduction of air at 750° C.

[0048] In air, the two steps become more distinct (see FIG. 5), but the
second of these coincides with the loss of carbon residue as carbon
dioxide. Accordingly, this second weight loss appears smaller in air at
64%, but this is only because it does not cover the full range of the
decomposition identified under nitrogen.

CONCLUSION

[0049] Analysis has shown that at low temperatures there are two clear
weight losses with PvdC. Evidence suggests the first around 130°
C. may be associated with residual moisture. The second decomposition
around 200° C. is consistent with dehydrochlorination of the PvdC.

[0050] The experimental analysis conveys that PvdC is a suitable material
for coating a laminate film forming at least part of an in-mould label.
The oxygen transmission (OTR) rates of films comprising PvdC and EVOH as
a function of room humidity (RH) were compared. The results are shown in
FIG. 6. The data plotted for the EVOH is literature values taken from the
Nippon Gohsei website for 29 mol % EVOH at 20° C. The data
obtained for PvdC is shown in table 3 below.

[0051] Sample 1 was a 58 μm 5-layer laminate polypropylene film coated
at a coat weight of 2.7 gsm with Diofan A036 commercially available from
Solvay SA.

[0052] Sample 2 was a 58 μm 5-layer laminate polypropylene film coated
at a coat weight of 2.7 gsm with Diofan B200 commercially available from
Solvay SA.

[0053] From FIG. 6, it can be seen that the EVOH containing film has a
generally low OTR and this remains generally constant from 0% to about
80% RH, at which point when the OTR begins to increase; a sharp increase
is seen from 90% to 100% RH, which simulates retort processing
conditions. The EVOH film does not perform well as an oxygen barrier at
high RH. The OTR of the PvdC film is shown to be generally low and
constant from 50 to 90% RH. Typical retort conditions for barrier
modelling are shown in FIG. 7 (time versus temperature graph).

[0054] A label comprising a PvdC coated laminate film for in-mould
labeling is less susceptible to the problems associated with "retort
shock" for the reasons provided herein.

[0055] The above described in-mould labels are greatly advantageous over
traditional labels to be applied to an article after manufacturing
thereof in that, on the one hand, the label is intimately bonded to the
article and, therefore, highly resistant to ripping and, on the other
hand, in terms of logistics because the polymeric articles to be labelled
do not need to be stored and transported to the premises where
traditional labels are to be applied. Among the many shortcomings of the
prior art are that labels become easily scratched; there is not a solid
bond between the label and the plastic part which results in peeling;
and, the part is not recyclable for the reason that the labels are not
compatible with the underlying plastic piece. Additionally, there is
added cost to the process of applying the label since it must be handled
once for the moulding process and a second time to add the label.

[0056] In-mould labelling using labels comprising PvdC addresses these
deficiencies in that the labels do not get scratched easily because they
are more durable in adverse conditions (compared to traditional stick-on
labels); peeling does not result due to the integral bond between the
label and the moulded article; the label is not subject to fading under
UV rays; the labels is compatible with the material of the article and,
therefore, recycling of the entire product is possible, in keeping with
environmentally friendly practice. The final product is also cleaner and
more sanitary than prior art products because less handling of the label
is involved during in-mould labelling.

[0057] A further advantage may be considered as the combination of using a
PvdC coated laminate film in an in-mould labelling process.

[0058] The polyvinylidene chloride surface may be printable. Suitable text
or graphic can thus be illustrated on the article.

[0059] The polyvinylidene chloride surface may be printed with a
heat-resistant ink. The ink may, therefore, withstand the elevated
temperatures during the moulding process.

[0060] The polyvinylidene chloride coat may have a coat weight of at least
about 1 gsm preferably from about 1.5 gsm to about 4 gsm, more preferably
from about 1.8 gsm to about 3.7 gsm, and most preferably from about 2 gsm
to about 3.5 gsm. Barrier properties of the film will generally be
improved by higher coat weights, but such considerations must be balanced
by the possibly conflicting considerations of cost, aesthetics and other
types of (non-barrier) functionality.

[0061] The film substrate may comprise a polyolefin film, for example
polyethylene, polypropylene, mixtures thereof, and/or other known
polyolefins. The polymeric film can be made by any process known in the
art, including, but not limited to, cast sheet, cast film and blown film.
The film substrate may be of monolayer or of multi-layer construction.
This invention may be particularly applicable to films comprising
cavitated or non-cavitated polypropylene films, with a polypropylene core
and skin layers with a thickness substantially below that of the core
layer and formed for example from co-polymers of ethylene and propylene
or terpolymers of propylene, ethylene and butylene. The film may comprise
a biaxially orientated polypropylene (BOPP) film, which may be prepared
as balanced films using substantially equal machine direction and
transverse direction stretch ratios, or can be unbalanced, where the film
is significantly more orientated in one direction (MD or TD). Sequential
stretching can be used, in which heated rollers effect stretching of the
film in the machine direction and a stenter oven is thereafter used to
effect stretching in the transverse direction. Alternatively,
simultaneous stretching, for example, using the so-called bubble process,
or simultaneous draw stenter stretching may be used.

[0062] Alternatively, the film core layer may comprise a polyester film, a
polyamide film, or an acetate film, for example.

[0063] The core layer may be non-cavitated, or may be cavitated if an
opaque film is desired.

[0064] Thus, the label of the invention preferably comprises a PvdC coated
substrate, wherein the substrate is preferably a polyolefin substrate,
for example a polypropylenic substrate such as BOPP. The substrate may be
a monoweb, or may have a multi layer construction, whether by
coextrusion, coating or lamination or any combination thereof. Preferred
substrates comprise a BOPP core and coextruded terpolymeric skin layers.
The substrate or the skin layers of the film may comprise additional
materials such as anti-block additives, opacifiers, fillers, UV
absorbers, cross-linkers, colourants, waxes and the like.

[0065] The film of the invention may be further treated, by corona
discharge treating for example, further to improve ink receptivity of the
film or of the skin layer of the film.

[0066] The label of the invention may be provided with other layers, such
as primer layers, print layers, overlaquers, and the like.

[0067] During in-mould labelling, the label may be held in position by at
least one of a vacuum, compressed air and static electricity.

[0068] The label may be placed into the mould by at least one of feeding
the label into the mould by means of a belt, the label falling under
gravity from a magazine into the mould, and placing of the label by a
handling unit, preferably a robot. Use of a robot minimises human error
and improves sanitation of the final product.

[0069] The label may cover the entire outer surface of the article. In
other embodiments, only a portion of the outer surface of the article may
be covered. Label coverage may be dependent on the intended use of the
article.

[0070] Embodiments of the present invention will now be described, by way
of example only, with reference to and as shown in the accompanying
drawings, in which: FIG. 1: is a graph illustrating weight loss of PvdC
at low temperatures under nitrogen; FIG. 2: is a graph illustrating
weight loss of PvdC at low temperatures in air; FIG. 3: is a graph
illustrating weight loss of PvdC recast from THF and THF/Water, under
nitrogen; FIG. 4: is a graph illustrating weight loss of PvdC in Nitrogen
(air introduced at 750° C.); FIG. 5: is a graph illustrating
weight loss of PvdC in air; FIG. 6: is a graph illustrating OTR at
varying RH for an EVOH film and PvdC film; FIG. 7: is a graph
illustrating typical retort conditions for barrier modelling; FIG. 8: is
a schematic drawing of PvdC coated laminate film which can form at least
part of a label for an in-mould labelling process according to the
invention; and FIG. 9: is an alternative PvdC coated laminate film which
can form at least part of a label for an in-mould labelling process
according to the invention.

[0071] With reference to FIG. 8, there is shown a PvdC coated laminate
film (15) which can form at least part of a label for in-mould labelling
(IML).

Preparation of Barrier IML Film (Solid White)

[0072] A three layer polymeric tube (1) was formed by co-extruding a core
layer (3) (comprising polypropylene homopolymer (HP420M or 101-GB08), 12%
of 70% TiO2, and 3% antistatic masterbatch containing a blend of
glycerol mono stearate and ethoxylated amine) with a layer of
polyethylene/polypropylene/polybutylene terpolymer (KV333--a random
copolymer comprising polypropylene/ethylene/butylene-1) as an outer skin
layer (5) (first sealing layer) on one side of the core layer (3), and on
the other side of the core layer (3) there is a laminating layer (7)
(KV349--a polypropylene-polyethylene/-polybutylene random terpolymer).
The tube (1) was cooled and subsequently reheated before being blown to
produce a three layer biaxially oriented film tube. The film tube (1) was
then nipped and laminated to itself (laminating layer to laminating layer
constituting one internal layer) spliced to form a laminated film with
five layers to provide a 58 μm thickness laminate film (9). The
laminate film (9) is also provided with a further layer of primer (11)
(NeoRez R610).

[0073] The laminate film (9) was then coated with a PvdC layer (13)
(Diofan B200) to produce the PvdC coated laminate film (15).

[0074] It will be understood that similarly constituted clear films may be
prepared as above, but with the omission of TiO2.

Preparation of Barrier IML Film (Matt White)

[0075]FIG. 9 illustrates an alternative PvdC coated laminate film (15b)
which is similar to that of FIG. 9, except that the outer skin layer (5b)
is constituted by a proprietary incompatible blend of polypropylene and
polyethylene (DUL3636). Similar reference numerals, therefore, denote
similar features. Again, a corresponding clear film may be prepared in
this manner, whilst omitting TiO2.

[0076] The PvdC coated laminate film of FIG. 8 or 9 may form at least part
of an in-mould label and used in a process as described below.